As the telecommunication industry prepares to deliver multimedia services to enterprise, residential and other commercial establishments via wireless access technologies, there arises the need for wireless base station architecture that can efficiently provide these services over a wide range of geographical areas.
FIG. 1 shows a representation of a telecommunications network comprising base stations 120, mobile switching center (MSC) 130, public switching network 140 and mobile terminals 150. Network 100 is designed to support communications to and from remotes terminals 150 that are located within coverage area of base stations 120. For example, if the remote terminals are mobile/cellular telephone then the network supports telephone communications to and from mobile phone users located within the network.
Base stations 120 are preferably distributed to provide seamless coverage. That is, base stations 120 are located such that, at any location within a total coverage range of the network, a remote terminal will be able to communicate with at least one base station.
FIG. 2 shows a representation of a network having a base station distributed in a manner to provide seamless coverage over the entire network range. The effective range of each base station 120 in network 100 is shown as a circle and is referred to as a cell site.
In FIG. 2, base stations 120 overlap and there are no locations within the interior of the network that are not covered by at least one base station. As shown in FIG. 2, some locations may be able to communicate with two different base stations, while other locations may be able to communicate with three different base stations.
The network 100 shown in FIG. 2 may use the IS-95 communication scheme which is based on code division multiple access (CDMA) modulation. According to the IS-95 standard for CDMA systems, each base station 120 is assigned a different pseudo noise (PN) offset to allow each base station to support different code channels. For example, each base station can support up to 64 different code channels with each channel being assigned one of 64 different CDMA sequences.
Under the IS-95 standard, for each omni-directional base station with one carrier, a forward link (transmissions from base station to mobile terminal) may have up to 61 traffic channels with one pilot sync and paging channel. Similarly, a reverse link (transmissions from mobile terminal to base station) also may have up to 63 traffic channels with one or more access channels. Each of the traffic channels is identified by a distinct user long code sequence and each access channel is identified by a distinct access channel long code sequence.
The availability of all these traffic channels in a base station introduces interference between the channels. The interference level increases as more channels are assigned until the level of interference adversely affects the integrity of the communications. Depending upon the circumstances, the interference can limit the number of mobile terminals capable of being supported at one time by a single base station.
One conventional solution for increasing base station capacity (as well as coverage area) relies on sectorizing. In sectorization, omni-directional cell sites are divided into multiple sectors to achieve the desired capacity and coverage. Sectorization provides a way to divide the total number of users into smaller groups. A sectorized antenna system uses directional antennas to divide the cell sites.
FIG. 3 is an exemplary illustration of a sectorized network in which each cell site 310, 320 and 330 is divided into sectors A–C. Each sector is assigned a different PN offset to handle mobile terminals within the sector. Each sector is given a different PN offset and its own pilot channel. Thus, in FIG. 3, each cell site 310, 320 and 330 transmits a corresponding number of different pilot channels, for each corresponding sector. Since each sector of a given cell site has its own PN offset, each sector is capable of supporting 64 different code channels. As a result, the sectorization scheme in FIG. 3 increases the number of remote mobile terminals that can be supported by a single base station.
FIG. 4 is an exemplary illustration of a conventional base station with multi-sector transmission capability. The base station shown in FIG. 4 supports the conventional circuit switching network implementation of the prior art. Base station 410 includes transceivers 420–424, channel cards 430–433, analog cards 440–443 and trunk cards 450–453. Base station 410 has multiple digital trunks to handle voice and data traffic for a multi-carrier and multi-sector cell site. Base station 410 is large enough to accommodate the maximum number of T1 digital trunks for specified maximum number of sectors and carriers. Base station 410 further has processing capabilities for specified maximum sectors and carriers.
For example, a 15 MHZ block in a PCS frequency band can include 11 CDMA carriers and each carrier can have up to 3 sectors. Thus, base station 410 would have about 11 T1 trunks for a large cell site. This also requires the base station to have enough rack space to accommodate other hardware resources such as channel cards, transceivers etc. Although having sectorizing capabilities enable the base station to support multiple remote terminals, the base station shown in FIG. 4 has the disadvantages of being too bulky, costly and not scalable.
With the shift in the paradigm from conventional circuit-switched and voice-oriented wireless applications to packet-switched and high speed data-oriented wireless applications, it is essential to find cost-effective and modular approaches to build base stations which are easily scalable to handle multi-sector/multi-carrier that handle high capacity multi-media information.
Thus, it is desirable to have a system and a method for handling remote access requests to a CDMA wireless enterprise system for system operation and maintenance management. There is a further desire to have a system for transmitting CDMA calls including voice and data over a communication pathway with a higher bandwidth such as the internet. It is further desirable to have a CDMA system that handles the transmission of calls, especially data calls, without the inherent difficulties of using a variety of transmission protocols for the same call. A need further exists for improved and less costly system which improves efficiency and the transmission rate and time of calls between a mobile unit and a base station and between base stations and a base station controller and between adjacent base stations.